Trace Downstream (Ready To Use)

Summary

Determines the path water will take from a particular location to its furthest downhill path.

Usage

• Tools in the Ready To Use toolbox are ArcGIS Online geoprocessing services that use hosted data and analysis capabilities in ArcGIS Online.

• For each input point a downstream trace line feature will be returned.

• An output downstream trace is the downstream path to the ocean. For example, an input point anywhere in the Mississippi River watershed will result in a down stream trace that ends in the Gulf stream.

• A downstream trace feature will not be returned if the point does not fall inside the extent of the specified data source.

• If no point identification field is specified, the unique ID field is used by default.

• The maximum number of input points is 1000. If more input features are provided, the service will return an error and will not execute.

• The pour point identification field must be of type integer or string. It is most useful to use a field consisting of unique values.

• The output downstream trace feature dataset has a field called PointID consisting of the values supplied in the point identification field. This allows the downstream trace to easily be related back to the input points.

• The resulting downstream trace feature dataset contains a field called LengthKm, which is the length in kilometers for each downstream trace.

• To provide feedback on this service, visit the Hydro forum.

Parameters

Dialog

Label	Explanation	Data Type
Input Points	The point features used for calculating downstream trace.	Feature Set
Point ID Field (Optional)	An integer or string field used to identify the input points. The default is to use the unique ID field.	Field
Data Source Resolution (Optional)	Specifies the source data resolution that will be used in the analysis. The values are an approximation of the spatial resolution of the digital elevation model used to build the foundation hydrologic database. Since many elevation sources are distributed in units of arc seconds, an approximation is provided in meters for easier understanding. Blank—The hydrologic source, built from a 3-arc second data source, which is approximately 90-meter resolution elevation data, will be used. This is the default. Finest—The finest resolution available at each location from all possible data sources will be used. 10 meters—The hydrologic source, built from a 1/3 arc second data source, which is approximately 10-meter resolution elevation data, will be used. 30 meters—The hydrologic source, built from a 1-arc second data source, which is approximately 30-meter resolution elevation data, will be used. 90 meters—The hydrologic source, built from a 3-arc second data source, which is approximately 90-meter resolution elevation data, will be used.	String
Generalize (Optional)	Specifies whether the output downstream trace lines will be smoothed into simpler lines or conform to the cell centers of the original DEM. Unchecked—The lines will not be smoothed. Each trace line of output downstream trace have more vertices since they conform to the original DEM cell centers. This is the default. Checked—The lines will be smoothed into simpler lines.	Boolean

Derived Output

Label	Explanation	Data Type
Output Trace Line	The output trace line features.	Feature Set

Python

arcpy.agolservices.TraceDownstream(InputPoints, {PointIDField}, {DataSourceResolution}, {Generalize})

Name	Explanation	Data Type
InputPoints	The point features used for calculating downstream trace.	Feature Set
PointIDField (Optional)	An integer or string field used to identify the input points. The default is to use the unique ID field.	Field
DataSourceResolution (Optional)	Specifies the source data resolution that will be used in the analysis. The values are an approximation of the spatial resolution of the digital elevation model used to build the foundation hydrologic database. Since many elevation sources are distributed in units of arc seconds, an approximation is provided in meters for easier understanding. Blank—The hydrologic source, built from a 3-arc second data source, which is approximately 90-meter resolution elevation data, will be used. This is the default. FINEST—The finest resolution available at each location from all possible data sources will be used. 10m—The hydrologic source, built from a 1/3 arc second data source, which is approximately 10-meter resolution elevation data, will be used. 30m—The hydrologic source, built from a 1-arc second data source, which is approximately 30-meter resolution elevation data, will be used. 90m—The hydrologic source, built from a 3-arc second data source, which is approximately 90-meter resolution elevation data, will be used.	String
Generalize (Optional)	Specifies whether the output downstream trace lines will be smoothed into simpler lines or conform to the cell centers of the original DEM. True—The lines will be smoothed into simpler lines. False—The lines will not be smoothed. Each trace line of output downstream trace have more vertices since they conform to the original DEM cell centers. This is the default.	Boolean

Derived Output

Name	Explanation	Data Type
OutputTraceLine	The output trace line features.	Feature Set

Environments

This tool does not use any geoprocessing environments.